The objective of this study addresses two aims; 1)to characterize the psychobiological correlates of response to CBT and 2)to clarify the state dependence of selected neurobiological disturbances across the course of the illness. It has been determined that clinical severity, an abnormal EEG sleep profile and increased HPA activity are associated with poorer response to DBC which suggests that some unipolar depressed patients may require somatic treatment in order to correct/control dysregulated CNS processes.